应用于局域表面等离激元共振扫描显微探针的球形Au@Ag纳米粒子的合成及介电敏感性检测

Spherical Au@Ag Nanoparticles for Localized Surface Plasmon Resonance Scanning Probes: Synthesis and Dielectric Sensitivity

局域表面等离激元共振(LSPR)显微探针的检测灵敏性主要取决于针尖上修饰的纳米粒子的LSPR性质.本文采用阴离子辅助法,在水溶液中通过调节Au核与Ag+的物质的量之比,实现Au核上不同厚度的Ag壳层包覆,可控地一步合成均一性好、银壳层较厚(≥10 nm)的核壳比不同的球形Au@Ag纳米粒子.通过扫描电镜(SEM)、透射电镜(TEM)及扫描透射电子显微镜X射线能谱(STM-EDS)线扫描分析对不同核壳比的Au@Ag纳米粒子进行形貌组成表征,证实了所合成核壳结构的可控性.将不同核壳比的Au@Ag纳米粒子置于不同折射率溶液中进行纳米粒子介电敏感性的研究,表明7.5 nm Au@28 nm Ag的纳米结构具有最高的品质因子.同时将不同核壳比的Au@Ag纳米粒子置于不同折射率的非导电性基底上进行单颗纳米粒子散射性质的研究,结果表明7.5 nm Au@28 nm Ag纳米粒子适合作为LSPR显微探针的高检测灵敏性纳米结构之一.

The detection sensitivity of localized surface plasmon resonance（LSPR） microscopic probes is mainly determined by the LSPR property of the modified metal nanoparticle at the end of the probe. In this paper, spherical Au@Ag nanoparticles（NPs） with good size uniformity and a thick Ag shell（≥10 nm） were synthesized using the anion-assisted one-step synthesis method in aqueous solution, and the thickness of the Ag shell can be controlled by simply adjusting the molar ratio of Au to Ag in the solution. We characterized the morphology and composition of Au@Ag NPs with different core-shell ratios by scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy（STEM-EDS） line scanning analyses, which confirmed the controllable synthesis of Au@Ag core-shell NPs by this method. Measurement of the dielectric sensitivity of Au@Ag NPs with different core–shell ratios in different refractive index solutions showed that the core-shell nanostructure of7.5 nmAu@28 nmAg has the highest figure of merit for detection. Further investigation of the plasmonic properties of a single Au@Ag NP on nonconductive substrates with different refractive indexes confirmed that7.5 nmAu@28 nmAg NPs are one of the most suitable candidates for dielectric sensing in LSPR microscopy among the spherical Au@Ag NPs.